Lead fixation devices for securing a lead to a cranium

ABSTRACT

A lead fixation device for securing a first portion of a lead relative to a hole formed through a skull includes a skull attachment member having an upper surface and a lower surface and a bore extending through and between the upper surface and the lower surface. The lead fixation device also includes a lead compression mechanism integral with the skull attachment member and aligned with the bore of the skull attachment member. The lead compression mechanism defines a passageway through the lead fixation device, which passageway is characterized by a diameter that is defined by the lead compression mechanism. The lead compression mechanism is configured to transition the diameter from a first size to a second size greater than the first size upon insertion of an implant tool through the passageway, and from the second size to the first size upon removal of the implant tool from the passageway.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to U.S. ProvisionalPatent Application Ser. No. 62/773,121, filed Nov. 29, 2018, for “LeadFixation Devices for Securing a Lead to a Cranium,” the entiredisclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to apparatuses and methods usedwhen implanting a medical device in a patient, and more particularly, tolead fixation devices for securing a lead to a cranium and methods forusing the same.

BACKGROUND

Some diagnostic or interventional medical procedures require implantingone or more leads through a hole in a patient's cranium. Once thesurgeon places a lead so that the distal end is at a desired location,the surgeon wants the lead to stay there for whatever ultimate medicalpurpose the lead has, for example, to monitor physiological parametersfrom a patient or to deliver a therapy to the patient. Usually, however,there are steps subsequent to placing the lead that are necessary tocomplete the surgical procedure, and some of these may cause inadvertentdisplacement of the lead away from the desired location, which may notbe corrected easily or efficiently.

Generally, leads may be provided with electrodes configured to senseinformation from the brain or to deliver a form of stimulation to thebrain intended to modulate neural activity, such as electricalstimulation. The sensing and/or stimulation may occur at a distal end ofthe lead, for example, through electrodes exposed to brain tissue at adistal end, wherein the signals are communicated through conductorsdisposed in the lead body extending to a lead proximal end. Connectionsavailable at the lead proximal end allow the lead to be connected toanother medical device, implanted or external, that processes the sensedsignals and/or generates the form of stimulation.

For example, in the responsive neurostimulation system manufacturedunder the tradename RNS SYSTEM by NeuroPace, Inc., the proximal ends ofone or more implanted brain leads can be connected to another implantedmedical device, namely a neurostimulator that is seated in a tray orferrule in a craniectomy in the patient's skull. In another example, theleads may be implanted in a patient so that an intracranial monitoringprocedure can be undertaken for a period (e.g., several days or a coupleof weeks), with the proximal ends of the implanted leads being connectedto external equipment monitoring the patient's brain activity, such asto identify a focus or the foci of epileptiform activity in the patient.

There are multiple types of brain leads currently available. Inapplications where the leads are being used to sense or stimulate braintissue at or near the focus of undesirable epileptiform activity, thereis a depth lead (also sometimes referred to as a “deep brain lead” or asa “stereotactic depth lead”, because this lead type is often implantedusing stereotaxy, a three-dimensional localization and placementprocedure) and a cortical strip lead (also known simply as a “corticallead” or as a “subdural lead”, because this lead type is usuallyimplanted underneath the dura mater).

A depth lead is implanted so that the distal end is located in the braintissue, in or adjacent a structure that is deemed to be associated withthe generation of the undesirable activity. A cortical strip lead isimplanted so that the distal end lays on a surface of the brain at oradjacent brain tissue that is believed to comprise an epileptic focus.The intended location of the distal end of the brain lead in or on thebrain is referred to hereinafter as the “target”.

A lead manufacturer may make different lead types in one or morestandard lengths, rather than in lengths customized for a particularapplication in a particular patient. In addition, the depth lead typemay be intended to be implanted using stereotactic equipment or someother tool that requires some length in excess of that which is neededto extend from the cranium and the connection to another medical deviceand the target (e.g., so that the lead is long enough to extend throughthe distance required when using a stereotactic frame mounted to thepatient). For at least the reason that a lead may be manufactured tohave more length than is necessary to traverse the distance between theproximal connection to another implant or external equipment and thetarget, brain leads are often manufactured to be quite flexible. Thatis, if the lead is flexible, excess length can be coiled or folded atthe surface of the skull before the scalp is replaced. Further,flexibility may be considered a better alternative than a stiff leadwhen the lead is to remain in place in or on a surface of the brainchronically, as opposed to acutely, such as to minimize tissue damageand to optimize the integrity or resolution of signals. Brain leadsmanufactured and sold with the RNS SYSTEM, for example, have aflexibility on par with that of a piece of cooked spaghetti.

When implanting a lead in the brain tissue, though, its relativeflexibility can present challenges when delivering the distal end to thetarget. Accordingly, a brain lead is often provided with an inner lumenthrough which a removable stiffener, such as a stylet, can be disposed.The stylet lends stability to the lead while the distal end is routed tothe target, and is then removed when the lead has been positioned whereit is intended to remain, either acutely or chronically. It isundesirable, however, if the act of withdrawing the stylet causes thedistal end to move away from the target.

Equipment or tools used in implanting a brain lead can alsounintentionally cause the distal end of a brain lead to move away fromthe target in procedural steps undertaken subsequent to placing thelead. For example, a slotted cannula is often employed in implantingleads stereotactically, in which a hole is formed in the patient's skullat a location calculated to allow an appropriate trajectory of a lead toa deep brain target. In one example of such a procedure, a frame isattached to the patient, and a guide tube is oriented to achieve thedesired trajectory relative to the skull hole. A cannula is insertedthrough the guide tube, such that its range of motion is constrained bythe guide tube. The cannula may be provided with a removable roddisposed in an inner lumen thereof. The cannula is advanced through theskull hole towards the target. The inner rod in the cannula preventstissue from backing up into the cannula while it is advanced.

When the cannula has been advanced to or approximate the target, theinner rod is removed and a depth lead inserted into the cannula lumen.The surgeon then advances the depth lead to the target. (Sometimes thedepth lead is marked in advance at a proximal location, for example,with a stop gauge, to provide feedback to the surgeon when the targethas been reached.) Once the distal end of the lead reaches the target,the cannula must be withdrawn from the brain and the lead must beextracted from the cannula, so the stereotactic equipment can beremoved. A cannula is often provided with a longitudinally-extendingslot with a width wide enough to accommodate the diameter of the leadbody for this purpose, i.e., so that the lead can be stripped away fromthe cannula using the slot, rather than having to retract the cannulaover the lead body. This allows the lead to be manufactured withsomewhat less excess lead length than if the lead had to be long enoughto retract the cannula over the very proximal end of the lead. As is thecase with withdrawing a stylet, it is undesirable if the act ofdisengaging the lead body from a cannula (or other apparatus used forstereotaxy) causes the distal end of the brain lead to move away fromthe target.

SUMMARY

The present disclosure relates to a lead fixation device for securing afirst portion of a lead relative to a hole formed through a skull. Thelead fixation device includes a skull attachment member having an uppersurface and a lower surface and a bore extending through and between theupper surface and the lower surface. The lead fixation device alsoincludes a lead compression mechanism that is integral with the skullattachment member and aligned with the bore of the skull attachmentmember. The lead compression mechanism defines or forms a passagewaythrough the lead fixation device, which passageway is characterized by adiameter that is defined by the lead compression mechanism. The leadcompression mechanism is configured to transition the diameter from afirst size to a second size greater than the first size upon insertionof an implant tool through the passageway, and from the second size tothe first size upon removal of the implant tool from the passageway.

In one configuration, the compression mechanism is fixedly securerelative to the skull attachment member so that transition of thediameter between the first size and the second size results from radialoutward compression of the compression mechanism and radial inwardexpansion of the compression mechanism relative to an axis through thepassageway. The first portion of the lead has a diameter and the firstsize of the diameter of the compression mechanism is less than thediameter of the lead to thereby secure the first portion of the lead inplace at the skull hole.

The present disclosure also relates to a lead fixation device forsecuring a portion of a lead relative to a surface of a skull. The leadfixation device includes a skull attachment member having an uppersurface and a lower surface. The lead fixation device also includes alead compression mechanism that is integral with the skull attachmentmember. The lead compression mechanism is formed of a flexible materialwhile the skull attachment member is formed of a material more rigidthan the lead compression mechanism. The lead compression mechanismforms a passageway through the skull attachment member. In oneembodiment, the passageway is characterized by a slot that faces in thedirection of the lower surface and extends along the length of thepassageway. In another embodiment, the passageway is characterized by aslot that faces in the direction of the upper surface and extends alongthe length of the passageway.

The lead compression mechanism is formed of a flexible material and isconfigured to transition a width of the slot from an initial size thatis less than the diameter of the portion of the lead, to an expandedsize that is greater than the initial size upon receipt of appropriatelydirected first forces in a region of the lead compression mechanism thatforms the passageway. Such first forces increase the width and allow forthe portion of the lead to slide into the passageway. The leadcompression mechanism is further configured to transition the width ofthe slot from the initial size to a collapsed size upon receipt ofappropriately directed second force in a region of the lead compressionmechanism that forms the passageway. Such second forces decrease thewidth and secure the portion of the lead inside the passageway.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of apparatuses and methods will now be presented in thedetailed description by way of example, and not by way of limitation,with reference to the accompanying drawings, wherein:

FIG. 1A is a schematic of a patient's cranium showing implantedcomponents of a neurostimulation system, including leads and aneurostimulator, and related surgical accessories, including a burr holecover and a lead fixation plate.

FIGS. 1B and 1C are illustrations of known burr hole covers.

FIG. 1D is an illustration of a known lead fixation plate.

FIG. 2 is an illustration of some components of stereotactic equipmentthat may be used in a standard stereotactic procedure with a frame toimplant a depth lead in a patient's brain.

FIG. 3 is an illustration of a cannula (with a depth lead insertedtherein) that may be used during a procedure for implanting a depthlead.

FIGS. 4A-4D are illustrations of a first embodiment of a lead fixationdevice for securing a lead at a hole in a skull and on a surface of theskull.

FIGS. 5A-5C are illustrations of a skull attachment member of the leadfixation device of FIGS. 4A-4D.

FIG. 6 is a side view drawing of the skull attachment member of FIG.4A-4D.

FIGS. 7A and 7B are illustrations of a compression mechanism of the leadfixation device of FIGS. 4A-4D.

FIGS. 8A and 8B are illustrations of a locking member of the leadfixation device of FIGS. 4A-4D, that secures the compression mechanismin place in the skull attachment member.

FIGS. 9A and 9B are illustrations of a second embodiment of a leadfixation device for securing a lead at a hole in a skull and on asurface of the skull.

FIG. 10A-10J are illustrations of a lead implant procedure using thelead fixation device of FIGS. 4A-4D.

FIGS. 11 and 12 are illustrations of a first embodiment of a leadfixation device for securing a lead on a surface of the skull.

FIG. 13 is an illustration of a lead implant procedure using the leadfixation device of FIGS. 11 and 12.

FIGS. 14, 15A, and 15B are illustrations of a second embodiment of alead fixation device for securing a lead on a surface of the skull.

FIGS. 16A and 16B are illustrations of a lead implant procedure usingthe lead fixation device of FIG. 14.

DETAILED DESCRIPTION

Disclosed herein is a lead fixation device that allows the body of abrain lead to be secured relative to a hole formed through the skull andat the surface of a patient's skull while a stiffening element, such asa stylet, remains in place in a lumen of the lead body. The stiffeningelement thus can be withdrawn from the lead after the lead fixationaccessory is in place, reducing the likelihood that the act of pullingout the stylet will displace the distal end of the implanted lead awayfrom the target. Also disclosed herein are embodiments of lead fixationdevice that allow the body of a brain lead to be secured at or along asurface of a skull at a location between the point where the lead bodyexits the skull and the point where the lead connects to an implantedmedical device.

The embodiments are described primarily with reference to the lead beingan electrode-bearing lead, as might be used in an application for deepbrain stimulation or direct brain stimulation such as the responsivestimulations applications by NeuroPace, Inc. of Mountain View, Calif. Itshould be appreciated, however, that the lead fixation devices may beused with good results to secure a segment of a different type ofmedical device, such as a catheter or other medical instrument (with adiameter compatible with the accessory), relative to a surface of theskull prior to and/or during use of the medical device in its intendedapplication.

Overview of Procedures to Implant Brain Leads

For purposes of illustration, procedures to implant a depth lead and acortical strip lead will be described with reference to a responsiveneurostimulation system, in which a surgeon commonly uses both leadtypes.

With reference to FIG. 1A, a neurostimulator 110 and leads 120, 130 of aresponsive neurostimulation system are shown schematically, implanted ina patient. To implant a lead, the surgeon needs access to the brain. Asurgeon may gain access to the brain for purposes of implanting a leadby creating an opening through the skull. A opening may be created bydrilling a hole through the skull, by performing a craniotomy(temporarily removing a bone flap from the skull and replacing the flapafter access to the brain is no longer needed) or by performing acraniectomy (permanently removing a bone flap from the skull). Suchopening may be used exclusively for lead implant purposes, or may beused for another/additional purpose (for example, the surgeon can firstdeliver a lead to a target through an opening formed as part of acraniectomy, then use the same opening to implant another medicaldevice, such as a neurostimulator). The term “skull hole” is used hereinto refer to any category of opening formed in a patient's skull to gainaccess to the subdural spaces and to the brain.

In FIG. 1A, three skull holes have been formed: a burr hole 140 forpurposes of implanting a depth lead 120, a craniotomy 150 for purposesof implanting a cortical strip lead 130, and a craniectomy 160 in whicha ferrule or tray 112 and a neurostimulator 110 are ultimatelyimplanted. More particularly, the surgeon may use an air-powered drillto form an annular burr hole 140 of a diameter between 5-30 mm, with 14mm being a commonly-used diameter, for purposes of implanting a depthlead 120. Using appropriate tools, the surgeon may also perform acraniotomy 150 for purposes of implanting a cortical strip lead 130, andadditionally a craniectomy 160 in which to ultimately situate aneurostimulator at the patient's skull.

In FIG. 1A, a distal portion 122 of the depth lead 120 extends into thepatient's brain tissue from a 14-mm burr hole 140, and a proximalportion 128 extends proximally from the burr hole where it is plugged inat a proximal end 129 to a connector 114 of an implanted neurostimulator110. A distal portion 132 of a cortical strip lead 130 extends from afissure like hole or opening 151 at an edge of the craniotomy 150 onto asurface of the patient's brain, between the brain and the dura mater(not shown), and a proximal portion 138 extends proximally from the holewhere it is plugged in at a proximal end 139 to the connector 114. Theneurostimulator 110 has a strain relief 116 in the location where theproximal ends 129, 139 of the leads connect, to discourage the leadsfrom unintentional disconnection.

A distal end 124 of the depth lead 120 includes a plurality ofelectrodes 126 (three are shown in FIG. 1A), that can be used either forsensing electrographic activity from the brain or for delivering atherapy of electrical stimulation to it in an effort to modulate neuralactivity (e.g., lessen the severity of a seizure). Conductors extendingthe length of the lead body (not shown) and connected at the connector114 to the neurostimulator 110 allow the neurostimulator to process thesensed signals and to generate the stimulation signals. A distal end 134of the cortical strip lead 130 ends in a paddle 136 that, on abrain-facing surface thereof (not shown in FIG. 1A), exposes anotherplurality of electrodes (e.g., four) to the brain surface underneath thedura mater. These electrodes are also in electrical communication withthe neurostimulator 110 via conductors in the cortical strip lead 130and the connection at the connector 114.

In addition to the burr hole 140 or the craniotomy 150 opening 151, alead, especially of the cortical strip lead type, may be implanted usinganother opening in the cranium. More specifically, to implant theneurostimulator 110, the surgeon cuts a craniectomy 160 hole using atemplate that approximates the shape of the neurostimulator. The surgeonfits a tray or “ferrule” 112 into the hole and attaches or otherwisesecures it to the cranium, for example, using bone screws and/or foldingtabs 118 providing on the tray. The surgeon then situates theneurostimulator 110 into the tray 112. However, before placing the tray112, the surgeon can use the craniectomy 160 hole to implant a corticalstrip lead, such as the cortical strip lead 130, and then connect theproximal end thereof to the neurostimulator connector. (FIG. 1A does notshow any lead implanted using the craniectomy 160 in which the tray 112and neurostimulator 110 are situated.)

Both of the implanted leads 120, 130 in FIG. 1A are shown secured withknown lead fixation accessories. The depth lead 120 implanted throughthe burr hole 140 is shown secured with a burr hole cover 144 whichsubstantially fills the 14-mm diameter burr hole except for an aperturetherethrough that permits passage of the lead body. Examples of leadfixation accessories designed for burr holes are illustrated in FIGS. 1Band 1C.

Some burr hole lead fixation devices are designed for use withmechanical parts that need to be actuated in order to achieve fixationof the lead body, and others rely on friction fit or compression tolimit movement of the lead relative to the device. Some require at leastone element of the accessory to be put in place before a procedure toimplant a lead is begun. Some allow fixation only after any stiffeningelement used in implanting the lead has been removed. With reference toFIG. 1B, a burr hole lead fixation accessory manufactured by Medtronic,Inc. under the tradename “STIMLOC” uses several interlocking parts tosecure a lead body. With reference to FIG. 1C, a two-piece burr holecover manufactured by NeuroPace, Inc. relies in part on fitting aportion of the lead body into a groove in base element to reduce thelikelihood that further manipulation of the lead portion extendingproximally of the skull hole (e.g., to connect the lead to an implantedneurostimulator) will translate to movement of the distal end away fromthe target.

In FIG. 1A, the cortical strip lead 130 implanted through the craniotomy150, and having a proximal portion 138 extending from the opening 151 atan edge of the craniotomy onto the surface of the skull is secured at apoint on the lead body just proximal of where the lead body extends outof the hole, with a cranial plate 154. The cranial plate 154 is situatedover the lead body and then secured to the surface of the skull oneither side of the lead body with bone screws. Because of its shape, thetype of cranial plate 154 shown in FIG. 1A is commonly referred to as a“dog bone”. One such plate is shown in FIGS. 1D and 1 s manufacturedunder the tradename “MATRIXNEURO” by Synthes CMF. The cranial plate 154compresses the lead body to prevent lateral movement of the lead at thepoint of fixation to the skull. If the compression is inadvertentlyexcessive (e.g., by overtightening of the screws or by a patientpressing down on the plate), the integrity of the lead may becompromised (e.g., the conductors between the electrodes at the leaddistal end and the connector at the lead proximal end may be shorted).

The target for a depth lead 120 is usually more precise than the targetfor a cortical strip lead 130, at least in an application where thecondition is epilepsy. That is, the target for a depth lead 120 isusually a particular structure in the brain, such as the subthalamicnucleus (STN) or the cingulate gyrus. The target for a cortical striplead 130 may be somewhat more forgiving of imprecision, that is, theelectrodes on the distal end 124 of the strip lead 130 may be destinedto cover the general area on the surface of the brain where epilepticactivity is believed to be focused. Thus, it may be especiallybeneficial to limit movement of the distal end of a depth lead once ithas been placed at the target.

In part because of the need for precision and in part because the leadis being implanted into brain tissue as opposed to on a surface of it, adepth lead 120 is most often implanted using some form of stereotaxy(e.g., with a frame affixed to the patient's skull or a “frameless”version of it). Stereotactic procedures are well known and will not bedescribed herein to any great degree. Briefly, however, one commonmethod uses frame-based stereotaxis to approach a target or targetsthrough a skull hole. The patient is given a local anesthetic and arigid frame or fixation device is attached to the patient's head, andthe brain is imaged (e.g., with a CT scan). The location of thetarget(s) is calculated based on a ‘co-registration’ of the images andthe frame, fiducials or other registered points on the head. Then, thepatient is sedated for surgery, the scalp is incised, and one or moreskull holes are formed in the patient's cranium, each at a location thatwill allow an appropriate trajectory to the deep brain target(s).

A hole in the skull is often formed with some standard diameter, owingto the drills typically available in the operating room to create it.When an air drill is used to create a hole in the skull with a diameterof 5 mm or greater, the skull hole is often referred to as a “burrhole.” Surgeons create standard-sized burr holes, because there aresurgical accessories intended for use with burr holes that are intendedfor use with certain burr hole diameters, such as 14 mm. However, thediameter of a brain lead may be much smaller than that of a burr hole,because 14 mm is on the order of ten times greater than the diameter ofthe lead to be implanted. For example, some brain leads manufactured byNeuroPace, Inc. have a diameter of only 1.27 mm. Therefore, in somecases a surgeon may choose to use a smaller diameter hole through whichto implant a lead. For example, a surgeon may choose to use a hand-heldtwist drill to create a hole with a diameter on the order of less than 5mm (depending on the diameter of the twist drill bit: a common oneresults in a 3.2 mm diameter hole). A skull hole formed using a twistdrill is sometimes referred to as a “twist drill hole”.

Referring now to FIGS. 2 and 3, part of the stereotactic equipment 200is secured to the patient's skull using a frame, a portion of which isshown as a graduated element 202 in FIG. 2, and a guide tube 204 isoriented to provide the desired trajectory. The guide tube 204 has aninner lumen of sufficient diameter to receive a cannula 304. The cannula304 is also formed as a cylinder, typically made of a metal, such asstainless steel, and has an inner lumen with a diameter sufficient toslidably receive first an inner rod (not shown) and thereafter a depthlead (the distal end 324 of a depth lead 320 is shown in FIG. 3).

The cannula 304 may be provided with a slot 306 running along its entirelength so that the lead body can be extracted from the cannula withouthaving to retract the cannula over the proximal end 330 of the lead.Thus, if the cannula 304 is slotted, the slot 306 must be dimensioned soas to allow the proximal portion of the depth lead 320 that extendsproximally of the skull hole to be separated from the cannula throughthe slot. The depth lead 320 also has an inner lumen running throughmost of the length of the lead in which a stiffening element, such as astylet, is removably disposed. (In FIG. 3, a stylet 302 is shownextending proximally of the depth lead 320). The stylet 302 may have aplastic member or stylet handle 303 at its proximal end that the surgeoncan grab to more easily extract the stylet from the lead inner lumen.

One or more stop gauges may be configured so that they can encircle theproximal portion of either or both of the cannula 304 or the depth lead320 to guard against advancing the distal end of the cannula or thedepth lead beyond the target (not shown in FIG. 2 or 3). For example,the depth lead 320 may be measured in the operating room to identify alocation on a proximal portion that, once the lead is being routed tothe target, the surgeon can use to gauge when the lead has been advancedfar enough (or to some not-to-exceed distance) into the tissue. Thislocation on the proximal portion can be demarcated by fitting a stopgauge 310 around the lead body.

Manipulating the appropriate controls on the stereotactic equipment, thecannula 304 with the inner rod (not shown) in place is advanced into thebrain. The inner rod discourages brain tissue from backing up into thecannula lumen as the cannula creates a path to the target for the lead.When the cannula 304 is advanced as far as intended, the surgeonwithdraws the inner rod, and replaces it with the depth lead 320, byinserting the distal end 324 of the depth lead (with the stylet 302 inplace) into the proximal end 312 (or top) of the cannula.

FIG. 3 shows a cannula 304 with a depth lead 320 inserted within thecannula inner lumen. A proximal portion 328 of the depth lead 320extends proximally of a proximal end 312 of the cannula 304, and adistal portion 322 of the depth lead extends distally of a distal end308 of the cannula 304. The stylet 302 is disposed in an inner lumen ofthe depth lead 320 and traverses substantially the full length of thedepth lead 320, except for the very distal end 324 thereof. The stylet302 is shown extending proximally of the proximal end 330 of the depthlead 320, with a stylet handle 303 at the proximal tip. The stylet 302lends sufficient stiffness to the lead 320 while it is being manipulatedduring the implant procedure (e.g., to insert it into the cannula lumen.The stylet handle 303 makes it easier to remove the stylet 302 from thelead 320 before the procedure is over. It will be appreciated that in atypical stereotactic procedure, even when the depth lead 320 is insertedinto the cannula 304 and after the lead distal end 324 has beendelivered to the target, there is enough excess lead length so that aportion of the lead body will extend proximally of the proximal end 312of the cannula, so that the lead at a point on the proximal portion 328thereof can be grasped above the proximal end 312 of the cannula 304.

After the step in the procedure where the surgeon has the distal end 324of the lead 320 where he or she wants it, the cannula 304 is removedwhile the lead is separated from the cannula through the slot 306. Afterthe cannula 304 is removed, it is undesirable for subsequent steps tomove the distal end 324 of the lead away from the target. But preventingthat from happening can be challenging because, after the cannula 304 isremoved, the stylet 302 in the inner lumen of the lead 320 still has tobe extracted from the lead body before the procedure is complete. Theforce applied in pulling out the stylet 302 may tend to retract thedistal end 324 of the lead along with it, so removing the stylet isanother step which may result in dislodging the lead away from thetarget.

Furthermore, some form of lead fixation device typically is used tosecure a proximal portion of the implanted lead at or near the skullhole or otherwise somewhere on the surface of the skull, to discouragerelative movement between the implanted distal portion of the lead andthe proximal portion of the lead after the procedure is complete. Thestep is another opportunity for unwanted displacement of the distal endof the lead from the target.

Lead Fixation Device with Compression Mechanism at Skull Hole

With reference to FIGS. 4A-9B, described are embodiments of a leadfixation device 400, 900 configured to compress against a lead body tothereby secure the lead body relative to a skull hole and prevent or atleast significantly reduce movement of the lead body either further intothe skull hole or out of the skull hole during implant of the lead. Thislead fixation device 400, 900 secures a first portion of the lead at askull hole where the part of the lead distal the first portion extendsthrough the skull hole in a direction transverse to the skull surface,and secures a second portion of the lead relative to a skull surfacesuch that the second portion rests on and along a skull surface, in aparallel arrangement with the skull surface. The lead fixation device400, 900 overcomes the lead implanting issues described above withreference to FIGS. 2 and 3, including in particular the issues of leadmovement during removal of a cannula 304 from around a lead 320 andremoval of a stylet 302 from a lead.

The lead fixation device 400, 900 includes a skull attachment member402, 902 configured to be secured to the skull and a flexiblecompression mechanism 406, 906 that is associated with the skullattachment member. The compression mechanism 406, 906 is configured tocompress radially outward to expand its inner diameter to receive a leadimplant tool, e.g., a cannula, and then expand radially inward to reduceits inner diameter to compress against a portion of the lead body uponremoval of the lead implant tool.

With continued reference to FIGS. 4A-9B, the skull attachment member402, 902 includes a central bore 410, 910 and lead securing featurescorresponding to surface channels 414, 914 formed in the body 415, 915of the of the attachment member and that extend from the central bore tothe outer perimeter 417, 917 of the attachment member. The skullattachment member 402, 902 may also include a pair of opposedprotrusions 416, 916 at a location along the length of each of thesurface channels 414, 914. These protrusions 416, 916 extend inwardtoward the center 419, 919 of the channel 414, 914 to provide an area ofreduced width of the channel that functions to secure a portion of alead body in place in the channel. The skull attachment member 402 alsoincludes a pair of screw holes 412, 912 for receiving bone screws 408,908 that secure the lead fixation device 400, 900 to the skull. The bonescrews 408, 908 may be preinstalled into the screw holes 412, 912 via aninterference fit, or they may be separately installed through the holesafter placement of the skull attachment member 402, 902.

With reference to FIGS. 6-8B, the compression mechanism 406 is locatedin a first recess 418 formed in the skull attachment member 402 thatsurrounds the central bore 410, and is secured in place by a lockingring 404 that fits in a second recess 420 that also surrounds thecentral bore. The skull attachment member 402 and the locking ring 404are formed of a rigid plastic, e.g., PEEK. The locking ring 404 includesa circular recess 430 sized to receive the compression mechanism 406.The diameter 432 of the recess 430 is slightly greater than the outerdiameter 426 of the compression mechanism to provide a space for radialexpansion of the compression mechanism and a corresponding increase inthe size of its inner diameter 424 when a cannula is inserted throughthe opening defined by the compression mechanism.

The compression mechanism 406 is formed of a flexible material, e.g.,silicone, and is configured such that the inner diameter 424 defined bythe compression mechanism expands to accommodate insertion of a cannula304 and contracts to fit tightly around a lead body (when the cannula isremoved from the compression mechanism) to prevent movement of the leadrelative to a skull hole. Properties of the compression mechanism,including the inner diameter 424, the outer diameter 426 and thecross-section diameter 428, and the stiffness of the compressionmechanism material may be selected to obtain the desired results.

While the compression mechanism 406, 906 in the embodiments in FIGS.4A-9B is in the form of an O-ring, other types of compression mechanismsare contemplated. For example, the compression mechanism may be definedby a slot with silicone on each side that defines a cross-section widththat compresses a portion of a lead body sufficiently to secure the leadin place in relative to a skull hole.

With reference to FIGS. 10A-10J, an example implant procedure for thelead fixation device 400 of FIGS. 4A-8B is provided. A twist drill hole440 is formed in a location of the cranium 444 using known stereotactictechniques. (See FIG. 10A.) The distal end of a split (or slotted)cannula 304 (with an inner rod 446 inserted) is slid through apassageway or bore 410 of the lead fixation device 400 that is definedby a compression mechanism 406 of the device. The size of thepassageway, which is defined by an expanded inner diameter 424 of thecompression mechanism 406, exerts sufficient radial pressure on thecannula 304 to hold the lead fixation device 400 in place on thecannula. (See FIG. 10B.)

The distal portion of slotted cannula 304 (with the inner rod 446inserted) it is inserted through the twist drill hole 440, into thebrain to a known depth using stereotactic techniques. (See FIG. 10C.)The lead fixation device 400 is slid down the cannula 304 in direction A(see FIG. 10c ) to rest on top of the cranium 444 and is secured inplace using bone screws 408. (See FIG. 10D.)

The inner rod 446 in the cannula 304 is removed by pulling on the innerrod 446 in direction B. (See FIG. 10E.) The lead 320 with a stylet 302inserted is inserted into the cannula 304 and advanced in direction C tothe known/predetermined depth using known stereotactic techniques. (SeeFIG. 10F.)

The cannula 304 is removed from around the lead 320 through the slot 306of the cannula. (See FIG. 10G.) Or, in other words, the lead 320 isseparated from the cannula 304 through the slot 306. When the cannula304 is removed, the size of the passageway of the lead fixation device400, which is defined by a slightly less expanded inner diameter 424 ofthe compression mechanism 406, shrinks into abutting contact with aportion of the lead 320 and applies enough inward force on the lead tosecure the lead in place at the twist drill hole 440 so the lead is notdisplaced in either distal or proximal direction.

The stylet 302 inserted in the lead 320 is removed from the lead indirection D. (See FIG. 10H.) The lead 320 is left secure in place by thecompression mechanism 406 and a proximal portion 328 of the lead 320 isavailable for routing to a neurostimulator can. (See FIG. 10I.) A secondportion 450 of the lead 320 is locked in place in a channel 414 of thelead fixation device 400 and routed along the surface of the cranium 444to a neurostimulator can; and bone screws 408 are then used to securethe lead fixation device 400 to the surface of the cranium 444. (SeeFIG. 10J.)

Thus disclosed is a lead fixation device 400, 900 for securing a firstportion 448 of a lead 320 relative to a hole 440 formed through a skull.The lead fixation device 400 includes a skull attachment member 402, 902having an upper surface 421 and a lower surface 423 and a bore 410, 910extending through and between the upper surface and the lower surface.The lead fixation device 400, 900 also includes a lead compressionmechanism 406, 906 that is integral with the skull attachment member402, 902 and aligned with the bore 410, 910 of the skull attachmentmember. Integral in this context means the lead fixation device 400, 900is formed of components assembled into a single assembly that cannot bedisassembled without damaging the structural integrity of one or more ofthe component parts.

The lead compression mechanism 406, 906 defines or forms a passageway425, 925 through the lead fixation device 400, 900, which passageway ischaracterized by a diameter 424, 924 that is defined by the leadcompression mechanism. The lead compression mechanism 406, 906 isconfigured to transition the diameter 424, 924 from a first size to asecond size greater than the first size upon insertion of an implanttool 304 through the passageway 425, 925, and from the second size tothe first size upon removal of the implant tool from the passageway.

In one configuration, the compression mechanism 406, 906 is fixedlysecure relative to the skull attachment member 402, 902 so thattransition of the diameter 424, 924 between the first size and thesecond size results from radial outward compression of the compressionmechanism and radial inward expansion of the compression mechanismrelative to an axis 427, 927 through the passageway 425, 925. The firstportion 448 of the lead 320 has a diameter and the first size of thediameter 424, 924 of the compression mechanism 406, 906 is less than thediameter of the lead to thereby secure the first portion of the lead inplace at the hole 440.

Thus, the functionality of the lead fixation device 400, 900 is impartedby compression and expansion of the compression mechanism and nodisplacement or movement of the compression mechanism up or down alongthe axis, or about the axis is required. In fact, no relative movementbetween the components of the lead fixation device 400, 900 occurs whensecuring a lead in place—other than compression and expansion of thecompression mechanism within the skull attachment member. This isdistinct from prior art burr hole fixation devices where movement of onepart, e.g., a lid or cap, relative to another part, e.g. a base, isrequired to secure a lead in place.

The compression mechanism 406, 906 is formed of a flexible material,e.g., silicone, that compresses from a normal state upon receipt offorce by the implant tool 304 and returns to the normal state in anabsence of such force. In one configuration, the lead compressionmechanism is an O-ring. In another configuration, the lead compressionmechanism is formed by a pair of structures on opposite sides of thebore 410, 910 of the skull attachment member.

The skull attachment member 402, 902 is formed of a material more rigidthan the lead compression mechanism. The skull attachment member 402,902 also includes at least one surface channel 414, 914 configured toreceive a second portion 450 of the lead proximal the first portion ofthe lead.

Lead Fixation Devices with Compression Mechanism Along Skull Surface

With reference to FIGS. 11 and 12, described is a first embodiment of alead fixation device 500 configured to compress against a lead body tothereby secure the lead body relative to a skull surface adjacent askull hole. The lead fixation device 500 prevents or at leastsignificantly reduces movement of the lead body either further into theskull hole or out of the skull hole during implant of the lead. Thislead fixation device 500 secures a portion of the lead relative to askull surface such that the portion rests on and along a skull surface,in a parallel arrangement with the skull surface.

The lead fixation device 500 includes a skull attachment member 502configured to be secured to the skull and a flexible compressionmechanism 506 that is associated with the skull attachment member. Thecompression mechanism 506 is configured to receive a portion of a leadbody through a slot 508 and then to compress against the portion of thelead body upon receipt of a compressive force.

The skull attachment member 502 is formed of a rigid plastic, e.g.,PEEK. The compression mechanism 506 is formed of a material, e.g.,silicone, that is softer and more flexible than the material of theskull attachment member. During production of the lead fixation device500, the skull attachment member 502 may be formed first with thecompression mechanism 506 being formed over and within recesses of theskull attachment member to produce an integral, single piece structurewith no moving parts. Integral in this context means the lead fixationdevice 500 is formed of components assembled into a single assembly thatcannot be disassembled without damaging the structural integrity of oneor more of the component parts.

With reference to FIG. 12, the compression mechanism 506 defines apassageway 504 through the skull attachment member 502. The passageway504 is provided by a c-shaped tube 507 having a slot 508 that extendsalong the length of the tube. The c-shaped tube 507 is characterized byan inner diameter 510 that is sized to receive a portion of a lead body.In one configuration, the slot 508 is characterized by an inner arc 512that extends between 25-35 degrees around the circumference of theinside of the c-shaped tube 507. As such, the width 514 of the slot 508is less than the inner diameter 510 of the tube 507.

The flexibility of the c-shaped tube 507, however, allows for theportions of the tube adjacent the slot 508 to deform upon receipt offirst forces 517 a, 517 b in the direction away from the axis 519 of thetube 507 and further separate from each to thereby allow a lead body tofit through the slot 508 to the interior of the tube. Once the lead bodyis in the interior of the c-shaped tube 507 and the first forces 517 a,517 b are removed, the deformed portions of the tube adjacent the slot508 return to their pre-deformed state and the c-shaped tube assumes itsnormal shape to secure the lead body within the interior of the tube. Inother configurations, the size of the inner arc 512 and the resultingslot 508 may be greater than or equal to the inner diameter 510 of thetube 507.

With continued reference to FIG. 12, in one configuration thecompression mechanism 506 includes a pair of wings 516 a, 516 b thatextend outward from a portion of the c-shaped tube 507 in oppositedirections. These wings 516 a, 516 b are formed of the same flexiblematerial as the c-shaped tube 507 and have a thickness of about 0.5 mm.When the lead fixation device 500 is secured to the skull by bonescrews, the flexibility of the pair of wings 516 a, 516 b allows them toflatten somewhat under the force of compression resulting from thescrewing down of the skull attachment member 502. This flatteningtranslates into a receipt of second forces 518 a, 518 b in the directiontoward the axis 519 of the tube 507. These second forces 518 a, 518 bcause the width 514 of the slot 508 in the area of the wings 516 a, 516b to reduce, which serves to further secure the lead in place andprevent movement of the lead body in either direction along the lengthof the tube 507. Compression of the silicone c-shaped tube 507 itselfalong the length of the tube may also serve to secure the lead in place.

With reference to FIG. 11, the compression mechanism 506 may alsoinclude a pair of circumferential grooves 520 a, 520 b configured tosecure a suture in place around the c-shaped tube 507. Sutures may thusbe applied at either end of the c-shaped tube to further secure the leadbody in place. However, given the above described functionality of thewings 516 a, 516 b, the use of sutures is optional as the second forces518 a, 518 b imparted by the wings by the securing of the device to theskull is sufficient to secure the lead in place and prevent movement ofthe lead body in either direction along the length of the compressionmechanism 506.

With continued reference to FIG. 11, the skull attachment member 502includes a pair of screw holes 522 a, 522 b configured to receive a bonescrew. The skull attachment member 502 has a maximum thickness of 2 mmin the region of the screw holes and tapers downward to a reducedthickness at the side edges.

With reference to FIG. 13, an example implant procedure for the leadfixation device of FIGS. 11 and 12 is provided. A twist drill hole 530is formed in location of the cranium using known stereotactictechniques. A lead 532 is implanted using known techniques.

The passageway 504 of the compression mechanism 506, as defined by ac-shaped tube 507, is aligned with the body of the lead 532 and aportion of the lead body is pushed through the slot 508 into thepassageway of the c-shaped tube. The lower surface 538 of the skullattachment member 502 is positioned relative to the skull surface toplace the wings 516 a, 516 b of the compression mechanism 506 on theskull surface.

The lead fixation device 500 is secured to the surface 544 skull usingbone screws 524. The screws are advanced into the bone to a levelsufficient to cause the pair of wings 516 a, 516 b to flatted and applysecond forces 518 a, 518 b that cause the width 514 of the slot 508 inthe area of the wings 516 a, 516 b to reduce, which serves to secure thelead in place and prevent movement of the lead body in either directionalong the length of the tube.

Thus disclosed is a lead fixation device 500 for securing a portion 534of a lead 532 relative to a surface 544 of a skull. The lead fixationdevice 500 includes a skull attachment member 502 having an uppersurface 536 and a lower surface 538. The lead fixation device 500 alsoincludes a lead compression mechanism 506 that is integral with theskull attachment member 502. Integral in this context means the leadfixation device 500 is formed of components assembled into a singleassembly that cannot be disassembled without damaging the structuralintegrity of one or more of the component parts. The lead compressionmechanism 506 is formed of a flexible material, e.g., silicone, whilethe skull attachment member 502 is formed of a material more rigid thanthe lead compression mechanism, such as PEEK.

The lead compression mechanism 506 forms a passageway 504 through theskull attachment member 502. The passageway 504 is characterized by aslot 508 that faces in the direction of the lower surface 538 andextends along the length of the passageway.

The lead compression mechanism 506 is formed of a flexible material,e.g., silicone, and is configured to transition a width 514 of the slot508 from an initial size that is less than the diameter of the portion534 of the lead 532, to an expanded size that is greater than theinitial size upon receipt of appropriately directed first forces 517 a,517 b in a region of the lead compression mechanism 506 that forms thepassageway 504. These first forces 517 a, 517 b may be respectivelyapplied against a facing edge of the c-shaped tube 507 in oppositedirection relative to the axis 519 of the passageway 504. As such, thefirst forces 517 a, 517 b increase the width 514 and allow for theportion 534 of the lead 532 to slide into the passageway 504.

The lead compression mechanism 506 is further configured to transitionthe width 514 of the slot 508 from the initial size to a collapsed sizeupon receipt of appropriately directed second force 518 a, 518 b in aregion of the lead compression mechanism 506 that forms the passageway504. These second forces 518 a, 518 b may be respectively applied alongan outer surface of the c-shaped tube 507 toward each other. As such,the second forces 518 a, 518 b decrease the width 514 and secure theportion 534 of the lead 532 inside the passageway 504. In oneconfiguration, the lead compression mechanism 506 includes at least onewing 516 a, 516 b that extends to a side of the passageway 504 and alongthe lower surface 538 of the skull attachment member 502. These wings516 a, 516 b function to distribute the second forces 518 a, 518 b alongthe c-shaped tube 507.

With reference to FIGS. 14, 15A, and 15B, described is a secondembodiment of a lead fixation device 600 configured to compress againsta lead body to thereby secure the lead body relative to a skull surfaceadjacent a skull hole and prevent or at least significantly reducemovement of the lead body either further into the skull hole or out ofthe skull hole during implant of the lead. This lead fixation device600, like the fixation device 500 described above with reference toFIGS. 11 and 12, secures a portion of the lead relative to a skullsurface such that the portion rests on and along a skull surface, in aparallel arrangement with the skull surface.

The lead fixation device 600 includes a skull attachment member 602configured to be secured to the skull and a flexible compressionmechanism 606 that is associated with the skull attachment member. Thecompression mechanism 606 is configured to receive a portion of a leadbody through a slot 608 and then to compress against the portion of thelead body upon receipt of a compressive force.

The skull attachment member 602 is formed of a rigid plastic, e.g.,PEEK. The compression mechanism 606 is formed of a material, e.g.,silicone, that is softer and more flexible than the material of theskull attachment member. During production of the lead fixation device600, the skull attachment member 602 may be formed first, with thecompression mechanism 606 being formed over and within recesses of theskull attachment member to produce an integral, single-piece structure.Integral in this context means the lead fixation device 600 is formed ofcomponents assembled into a single assembly that cannot be disassembledwithout damaging the structural integrity of one or more of thecomponent parts.

With reference to FIG. 14, the compression mechanism 606 defines apassageway 604 through the skull attachment member 602. The passageway604 is provided by a c-shaped tube 607 having a slot 608 that extendsalong the length of the tube. The c-shaped tube 607 is configured thesame as the c-shaped tube 507 described above with reference to FIGS. 11and 12. Thus, the c-shaped tube 607 is characterized by an innerdiameter 610 that is sized to receive a lead body. The slot 608 ischaracterized by an inner arc 613 that extends between 25-35 degreesaround the circumference of the inside of the c-shaped tube 607. Assuch, the width 614 of the slot 608 is less than the inner diameter ofthe tube 607.

The flexibility of the c-shaped tube 607, however, allows for theportions of the tube adjacent the slot 608 to deform upon receipt offirst forces 617 a, 617 b and further separate from each to therebyallow a portion of a lead body to fit through the slot to the interiorof the tube. Once the portion of the lead body is within the interior ofthe c-shaped tube 607 and the first forces 617 a, 617 b are removed, thedeformed portions of the tube adjacent the slot 608 return to theirpre-deformed state and the c-shaped tube assumes its normal shape tosecure the lead body within the interior of the tube.

The compression mechanism 606 may also include a pair of circumferentialgrooves 620 a, 620 b configured to secure a suture in place around thec-shaped tube 607. Sutures may thus be applied at either end of thec-shaped tube 607 to further secure the lead body in place and preventmovement of the lead body in either direction along the length of thetube. The skull attachment member 602 includes a screw hole configuredto receive a bone screw 612.

With reference to FIGS. 16A and 16B, an example implant procedure forthe lead fixation device of FIGS. 14, 15A, and 15B is provided. A twistdrill hole 630 is formed in location of the cranium 644 using knownstereotactic techniques. A lead 632 is implanted using known techniquessuch that a portion of the lead passes through the twist drill hole 630and is beneath the cranium 644 in the brain, and a portion of the leadrests on top of the cranium.

The compression mechanism 606 of a lead fixation device 600 is alignedwith the body of the lead 632 and a portion 634 of the lead body ispushed through the slot 608 into the compression mechanism. The skullattachment member 602 of the lead fixation device 600 is positionedrelative to the surface of the cranium 644 and is secured to the skullusing a bone screw 612. Sutures are secured around the pair ofcircumferential grooves 620 a, 620 b to secure the portion 634 of thelead 632 body in place in the compression mechanism 606 and preventmovement of the lead body in either direction along the length of thecompression mechanism.

Thus disclosed is a lead fixation device 600 for securing a portion 634of a lead 632 relative to a surface of a skull or cranium 644. The leadfixation device 600 includes a skull attachment member 602 having anupper surface 636 and a lower surface 638. The lead fixation device 600also includes a lead compression mechanism 606 that is integral with theskull attachment member 602. Integral in this context means the leadfixation device 600 is formed of components assembled into a singleassembly that cannot be disassembled without damaging the structuralintegrity of one or more of the component parts. The lead compressionmechanism 606 is formed of a flexible material, e.g., silicone, whilethe skull attachment member 602 is formed of a material more rigid thanthe lead compression mechanism, such as PEEK.

The lead compression mechanism 606 forms a passageway 604 through theskull attachment member 602. The passageway 604 is characterized by aslot 608 that faces in the direction of the upper surface 636 andextends along the length of the passageway.

The lead compression mechanism 606 is formed of a flexible material,e.g., silicone, and is configured to transition a width 614 of the slot608 from an initial size that is less than the diameter of the portion634 of the lead 632, to an expanded size that is greater than theinitial size upon receipt of appropriately directed first forces 617 a,617 b in a region of the lead compression mechanism 606 that forms thepassageway 604. These first forces 617 a, 617 b may be respectivelyapplied against a facing edge of the c-shaped tube 607 in oppositedirection relative to the axis 619 of the passageway 604. As such, thefirst forces 617 a, 617 b increase the width 614 and allow for theportion 634 of the lead 632 to slide into the passageway 604.

The lead compression mechanism 606 is further configured to transitionthe width 614 of the slot 608 from the initial size to a collapsed sizeupon receipt of appropriately directed second force 618 a, 618 b in aregion of the lead compression mechanism 606 that forms the passageway604. These second forces 618 a, 618 b may be respectively applied alongan outer surface of the c-shaped tube 607 toward each other. As such,the second forces 618 a, 618 b decrease the width 614 and secure theportion 634 of the lead 632 inside the passageway 604. The second forces618 a, 618 b may result from the placement and tying of a suture in eachof the grooves 620 a, 620 b.

The various aspects of this disclosure are provided to enable one ofordinary skill in the art to practice the present invention. Variousmodifications to exemplary embodiments presented throughout thisdisclosure will be readily apparent to those skilled in the art. Thus,the claims are not intended to be limited to the various aspects of thisdisclosure, but are to be accorded the full scope consistent with thelanguage of the claims. All structural and functional equivalents to thevarious components of the exemplary embodiments described throughoutthis disclosure that are known or later come to be known to those ofordinary skill in the art are expressly incorporated herein by referenceand are intended to be encompassed by the claims. Moreover, nothingdisclosed herein is intended to be dedicated to the public regardless ofwhether such disclosure is explicitly recited in the claims. No claimelement is to be construed under the provisions of 35 U.S.C. § 112,sixth paragraph, unless the element is expressly recited using thephrase “means for” or, in the case of a method claim, the element isrecited using the phrase “step for.”

What is claimed is:
 1. A lead fixation device for securing a firstportion of a lead relative to a hole formed through a skull, the leadfixation device comprising: a skull attachment member having an uppersurface and a lower surface and bore extending through and between theupper surface and the lower surface; and a compression mechanismintegral with the skull attachment member and aligned with the bore ofthe skull attachment member to form a passageway through the leadfixation device, which passageway is characterized by a diameter that isdefined by the compression mechanism, wherein the compression mechanismis configured to transition the diameter from a first size to a secondsize greater than the first size upon insertion of an implant toolthrough the passageway, and from the second size to the first size uponremoval of the implant tool from the passageway.
 2. The lead fixationdevice of claim 1, wherein the compression mechanism is fixedly securerelative to the skull attachment member so that transition of thediameter between the first size and the second size results from radialoutward compression of the compression mechanism and radial inwardexpansion of the compression mechanism relative to an axis through thepassageway.
 3. The lead fixation device of claim 1, wherein thecompression mechanism is formed of a flexible material that compressesfrom a normal state upon a receipt of force by the implant tool andreturns to the normal state in an absence of such force.
 4. The leadfixation device of claim 3, wherein the flexible material comprisessilicone.
 5. The lead fixation device of claim 1, wherein thecompression mechanism comprises an O-ring.
 6. The lead fixation deviceof claim 1, wherein the compression mechanism comprises a pair ofstructures on opposite sides of the bore of the skull attachment member.7. The lead fixation device of claim 1, wherein the first portion of thelead has a diameter and the first size of the diameter of thecompression mechanism is less than the diameter of the lead.
 8. The leadfixation device of claim 1, wherein the skull attachment membercomprises at least one surface channel configured to receive a secondportion of the lead proximal the first portion of the lead.
 9. The leadfixation device of claim 1, wherein the skull attachment member isformed of a material more rigid than the compression mechanism.
 10. Alead fixation device for securing a portion of a lead relative to asurface of a skull, the lead fixation device comprising: a skullattachment member having an upper surface and a lower surface; and acompression mechanism integral with the skull attachment member andforming a passageway relative to the skull attachment member, whichpassageway is characterized by a slot that extends along a length of thepassageway, wherein the compression mechanism is configured to:transition a width of the slot from an initial size to an expanded sizethat is greater than the initial size upon a receipt of appropriatelydirected first forces in a region of the compression mechanism thatforms the passageway, and transition the width of the slot from theinitial size to a collapsed size upon a receipt of appropriatelydirected second forces in a region of the compression mechanism thatforms the passageway.
 11. The lead fixation device of claim 10, whereinthe compression mechanism is formed of a flexible material.
 12. The leadfixation device of claim 10, wherein the portion of the lead has adiameter and the initial size is less than the diameter and the expandedsize is greater than the diameter.
 13. The lead fixation device of claim10, wherein the skull attachment member is formed of a material morerigid than the compression mechanism.
 14. The lead fixation device ofclaim 10, wherein the slot faces in the direction of the lower surfaceof the skull attachment member.
 15. The lead fixation device of claim14, wherein the compression mechanism comprises at least one wingextending to a side of the passageway and along the lower surface of theskull attachment member.
 16. The lead fixation device of claim 10,wherein the slot faces in the direction of the upper surface of theskull attachment member.